Mountain bikes are available in full suspension, or hardtail. Full suspension bikes have suspension in the front and rear, while hardtail bikes only have suspension in the front.
A 29 inch diameter wheel is larger, and is going to roll over things easier, but it’s heavier, so it doesn’t accelerate quite as fast.
As you go from entry level to midlevel to high level, the performance, braking, and shifting improve the more you spend.
When you look at full suspension and hardtail bikes in the same price range, you’re going to end up getting a little more bang for your buck with the hardtail because the pieces of the bike are going to be better. Whereas, with a full suspension, you will be paying more for the suspension as opposed to all the bike parts.
No matter your price range, a good way to get comfortable on the bike is to add a dropper post, which drops your saddle down and provides safety while going downhill or over big objects.
Gear ratios refer to the number of chainrings on the bike. There are two options: 1x or 2x, meaning one chainring or two chainrings. A 1x is more lightweight and easier to maintain, but doesn't have as many gear options. A 2x provides a lot of gear options, but it is a little bit heavier and there’s more maintenance required.